A tool arm assembly interfaces with and supports a tool to allow a human to easily manipulate the tool. A tool arm assembly may be coupled to a number of different systems, such as, for example, an exoskeleton, a stationary fixture such as a wall, or a mobile device such as a cart. A tool arm assembly typically includes one or more arm links that can move in a plane, such as a vertical plane, and intermediate links that couple the arm links and allow movement in another plane, such as a horizontal plane. With the flexibility provided by the multiple types of movement, a user may position the tool at precise locations.
An intermediate link allows arm links to rotate about an axis of rotation of the intermediate link. While this is useful for tool positioning, unintentional rotation of an arm link can occur when a user removes his hands from the tool, leading to safety issues and other problems as the tool moves in an unintended manner.